CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. 

 E. L. MARK, DIRECTOR. — No. 177. 



THE EFFECTS OF INBREEDING, CROSS-BREEDING, 



AND SELECTION UPON THE FERTILITY AND 



VARIABILITY OF DROSOPHILA. 



By W. E. Castle, F. W. Carpenter, A. H. Clark, S. O. Mast, and 



W. M. Barrows. 



Presented February 14, 1906. Received February 13, 1906. 



Contents. 



Page. 



Introduction 732 



Material and methods 733 



Brief history of the A series 735 



Low productiveness characteristic of the A stock 739 



Selections for high or low productiveness 740 



The M and N series 742 



Other families of Drosophila 743 



Effects of cross-breeding 743 



Experiments of A. H. Clark 743 



Experiments of W. E Castle 744 



Experiments of S. O Mast 747 



Experiments of W. M. Barrows 749 



Matings of cousins not more fruitful than those of brother and sister . . 751 

 Cyclical variations in fertility and their relation to external conditions and to 



inbreeding 751 



Further details concerning experiments of S. O. Mast 757 



History of the M and N series 757 



Crosses of series M and N with series A 761 



Selection for high or low productiveness 769 



Is a single copulation sufficient to fertilize all the eggs of a female' . . 770 

 Abstract of report of F. W. Carpenter on the sixth inbred generation of the 



A series 771 



The inbreeding experiments 771 



(a) Effect on fertility and sexual proportion 772 



(b) Effect on variability 772 



